Stable power generation even with little sun

Sanko Real Estate tried to construct this solar power plant by itself as much as it could without relying on consultants and others.

“Despite the difference between offices/condominiums and power plants, real estate companies are suited to plant construction because they can leverage expertise established through real estate development relatively well,” Nakamura said.

The deployed solar panel is the CIS solar cell manufactured by Solar Frontier K.K. Approximately 32,300 panels are installed. One of the factors behind the deployment was praise for the product’s reputation from another power producer who had earlier adopted the same panel. According to this source, the amount of generated power greatly outperformed the estimate indicated by the manufacturer.

“Despite our concern for the unusual adoption of CIS solar cells by 5MW-class plants, the amount of power generation has outperformed our expectations by more than 30%,” Nakamura said.

CIS solar panels are said to be superior in their amount of power generation during hours with little sunshine, such as the morning, late afternoon and cloudy days.

The output linearly rises toward peak hours with conventional crystalline silicon solar cells. With CIS solar cells, on the other hand, the output gradually rises toward peak hours. And it lowers little even when the output is low, which, as a result, leads to higher output compared with crystalline silicon solar cells.

As this feature makes a significant difference in Japan, where the amount of solar irradiation is limited and days and hours of power generation at peak output are also limited, CIS solar panels are expected to make it easy to secure a certain amount of power generation during the period from fall to spring.

Chiyoda Corporation designed and constructed the plant. Operation and maintenance is undertaken by Sanko Community, a 100% subsidiary of Sanko Real Estate, which is engaged in building/condominium maintenance, security and management.

Excluding GS Yuasa’s product for secondary batteries, the PV inverters used at the plant are TMEIC products. Sanko Real Estate initially planned to deploy a 1,000kW PV inverter manufactured by ABB of Switzerland, but changed its supplier to TMEIC due to various reasons including their reliability and support services.

The construction cost was reduced from the initially announced ¥2 billion (approx US$20.3 million) to about ¥1.6 billion. Of the ¥1.6 billion, about ¥1.2 billion is the cost of power generation facilities, and ¥400 million was used for land reclamation, etc.

PV inverters arranged in view of subdivision residents

The solar power plant faces south with a river running on the south side. In other words, the location is suited for a large-scale solar power plant because it allows to take in sunlight under good conditions and is free from concerns about buildings being built nearby that block the panels from sunshine.

The solar panels are set up about 70cm from the ground, tilted at 10°. According to Sanko Real Estate, the height and angle were optimum for the well-balanced intensity, cost and convenience for constructing the mounting system.

At this height and angle, the posts of the mounting system can be made short, and, as a result, constructors can set up the solar panels without using a stepladder, etc (Fig. 5). The mounting system is designed assuming wind speeds of up to 36m.

What is unique about this solar power plant’s design is the PV inverters positioned together in the center of the solar panels, which are neatly arrayed according to a grid system (Fig. 6). This represents consideration given to the residents of the adjoining subdivision who are concerned about operating noise and electromagnetic waves from the PV inverters. Positioning the PV inverters in the center of the plant also reduces the length of cable that connects the solar panels and PV inverters.